Balloon dilatation catheters are used to treat lesions in vessels. However, difficulties are encountered in navigating tortuous anatomy and safely crossing very tight lesions. Moreover, some lesions are difficult to dilate using just a balloon, and require a focused force to dilate the lesion at safe inflation pressures.
U.S. Pat. No. 6,394,995 to Solar et al. describes a system used to provide enhanced force to treat a lesion. This system has a flexible advancement member with a tracking member slidable over a guidewire, and a balloon having a distal end attached to the tracking member. But this type of system provides limited focused force and lacks pushability and maneuverability.